| APA | Smart Define. (2013). observation hole thesaurus. Retrieved September 28, 2026, from https://smartdefine.org/observation_hole/thesaurus/related |
| Chicago | Smart Define. 2013. "observation hole thesaurus" https://smartdefine.org/observation_hole/thesaurus/related (accessed September 28, 2026). |
| Harvard | Smart Define 2013, observation hole thesaurus, Smart Define, viewed 28 September, 2026, <https://smartdefine.org/observation_hole/thesaurus/related>. |
| MLA | Smart Define. "observation hole thesaurus" 18 May 2013. Web. 28 September 2026. <https://smartdefine.org/observation_hole/thesaurus/related> |